Prior art internal combustion engines typically employ a butterfly-type valve for throttling the volume of air admitted to the engine. Such a valve comprises a rotatable shaft mounted transversely of an engine manifold inlet and supporting a plate which may be rotated by the shaft to variably occlude the inlet.
In many applications, especially non-automotive, an engine may be required to operate for long periods of time at a substantially constant speed with variable load. For example, an electrical generator is ideally operated at 3600 rpm (60 Hz) to maintain 60 Hz power output. Also, an engine manufacturer may specify a particular engine speed as providing peak efficiency or peak power, for example, for use on a lawnmower or a shredder.
In the prior art, controlling an engine to a fixed speed under a variety of loads requires additional engine components such as vacuum or oil governor systems. Typically, these governor systems connect the throttle to a spring linkage and/or cable mechanism that adjusts the throttle angle of the butterfly valve plate to adjust the effective cross-sectional flow area of the inlet to meet the air flow requirement of the engine. Such systems typically are of low accuracy and add significant numbers of components, and thus cost and complexity, to an engine. Such systems are also prone to failure from clogging or damage by environmental debris such as grass, stones, and wood chips.
What is needed is a simple, inexpensive throttle control system for reliably and accurately controlling the speed of an internal combustion engine under varying load conditions.
It is a principal object of the present invention to control the speed of an internal combustion engine under varying load conditions.
It is a further object of the present invention to control the speed of an internal combustion engine at a fixed speed.
It is a still further object of the invention to increase the reliability and accuracy of fixed speed control of an engine.
It is a still further object of the invention to reduce the complexity and manufacturing cost of an internal combustion engine, and especially a small engine used for non-automotive purposes.